MongoDB - Get the sum of an object in an array

Question

Hi I'm very new to MongoDB, I'm trying to get the total price and promo of the below MongoDB data with document.collection.find and $add functionality:

Data:

[
  {
    "catalog":"A",
    "book":[
    {
      "title":"Mermaid yang terdampar",
      "price":90000,
      "promo":15000
    },
    {
      "title":"Srigala berbulu domba",
      "price":30000,
      "promo":15000
    }
  }
]

And my expected result would be sth like this:

[
  {
    "catalog": "A",
    "totalPrice": 140000,
    "totalPromo": 32000
  },
]

Does anybody ever encounter a similar issue? I'm confused with the query :)

Yong Shun · Accepted Answer · 2022-04-02 02:13:32Z

4

For .find() query, you can direct use the $sum operator.

db.collection.find({},
{
  catalog: 1,
  totalSum: {
    $sum: "$book.price"
  },
  totalPromo: {
    $sum: "$book.promo"
  }
})

Sample Mongo Playground

answered Apr 2, 2022 at 2:13

Yong Shun

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1 Comment

Yong Shun Over a year ago

No problem, this answer provides the sum of the book array for each document (calculate under each document). If you are looking for sum based on the catalog, you need the aggregation query with $group which covers in the other answer.

Kareem Adel · Accepted Answer · 2022-04-02 01:32:06Z

3

use aggregate

db.getCollection('myCollection').aggregate([
    { "$group": {
        "_id": "$tempId",
        "totalPrice": { 
            "$sum": { "$sum": "$book.price" } 
        },
        "totalPromo": { 
            "$sum": { "$sum": "$book.promo" } 
        }
    } }
])

answered Apr 2, 2022 at 1:32

Kareem Adel

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Comments

Sahil Thummar · Accepted Answer · 2022-04-02 02:30:47Z

0

Using $group (aggregation)

db.getCollection('catlog').aggregate([{ 
    $group: {
        _id: "$_id",
        catalog: { $first: "$catalog" },
        totalPrice: { "$sum": { $sum: "$book.price" } },
        totalPromo: { "$sum": { $sum: "$book.promo" } }
    }
}])

Output will be:

{
    "_id" : ObjectId("6247b33cffc5b6f714769fbb"),
    "catalog" : "A",
    "totalPrice" : 120000,
    "totalPromo" : 30000
}

answered Apr 2, 2022 at 2:30

Sahil Thummar

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